Update setup-pixi to v0.9.4 in stubtest job

Author: kkollsga

.github/workflows/ci-additional.yaml

@@ -211,7 +211,7 @@ jobs:
             pixi.lock
           key: ${{ needs.cache-pixi-lock.outputs.cache-id }}
 
-      - uses: prefix-dev/setup-pixi@v0.9.3
+      - uses: prefix-dev/setup-pixi@v0.9.4
         with:
           pixi-version: ${{ env.PIXI_VERSION }}
           cache: true